pre-merge issue with rm -rf node_modules

[ghost]

I like the idea of #35 a lot, but it caused me a problem. For pre-merge I want to remove all npm packages with rm -rf node_modules, and then reinstall them. But, then pre-git changes the package.json file again on reinstall, changing my settings in package.json (for instance, adding the commit script, which I don't want) and recreating the git hooks. I solved this by doing npm prune, npm update instead, which is probably better anyway… I think. It might be better to use this approach in the README.